The invention relates to cam dies, and more particularly to stepped cam die having at least one cam ring actuated by a cam actuator.
Sprockets are widely known and used as a means of transmitting power between shafts. Power transmission sprockets are made in several ways. Sheet metal types are fabricated by spinning or cam dies. In this method, the teeth or cogs are formed in a perpendicular motion of the die to the pre-form. Sprockets may also be formed by a punch and die system. A punch is used to axially press a work piece through a die.
Representative of the art is U.S. Pat. No. 3,796,085 to Fisher et al. which discloses a method for making sprockets by die drawing a disc into a cup shaped member while simultaneously forming the sprocket teeth thereon.
Also representative of the art is U.S. Pat. No. 5,269,167 to Gerhart which discloses an adjustable aerial cam unit for use in a power press. A slide block is slideably mounted at an angle relative to the plane of movement of the ram to move between extended and retracted positions.
The prior art methods suffer from creating a burr at the end of a part by relying solely on either on an in-and-out motion (horizontal) or on a vertical motion. Further, it is relatively complex requiring a plurality of moving parts as is found in multi-station fabrication, which necessarily adds cost to the finished part. Further, due to limitations in plastic flow, prior art methods of stamping complex forms in a single stroke limits the complexity of the shaped surface. The metal tears or wrinkles if it is formed beyond certain limits in a single stroke.
What is needed is a cam die that forms a sprocket by a lateral and vertical movement of a cam ring. What is needed is a cam die that comprises a plurality of coaxial cam rings. What is needed is a cam die to press form a toothed sprocket using multi-stage forming in a single pressing operation. The present invention meets these needs.
The primary aspect of the present invention is to provide a cam die that forms a sprocket by a lateral and vertical movement of a cam ring.
Another aspect of the invention is to provide a cam die that comprises a plurality of coaxial cam rings.
Another aspect of the invention is to provide a cam die to press form a toothed sprocket using multi-stage forming in a single pressing operation.
Other aspects of the invention will be pointed out or made apparent by the following description of the invention and the accompanying drawings.
The invention comprises a cam die. The cam die comprises at least one cam ring. The cam ring comprises a plurality of moveable cam teeth. The cam teeth are moveable on a normal toward an axis of the cam die by a cam actuator. The cam actuator has an inside diameter that is less than an outside diameter of the cam ring. As the cam actuator moves parallel to the cam die axis along an outside circumference of the cam ring, the cam teeth are progressively engaged and pressed inwardly toward a work piece. The work piece is moved simultaneously with the cam actuator by action of a punch that is concentric with the cam actuator and within the diameter of the cam ring. Each cam tooth is simultaneously engaged with the work piece as the work piece passes. A resilient member returns each cam tooth to a starting position after the cam actuator is withdrawn, allowing ejection of a finished part.